Nitric-acid concentration



Patented Dec. 24, 1929 UNITED STATES PATENT OFFICE RALPH H. HCKEE, .OF LEONIA, NEW JERSEY, ASSIGNOR TO SOUTHERN ELECTRO- CHEMICAL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY NITRIC-ACID CONCENTRATION no Drawing.

p This invention is an improvement in processes of concentrating n1tr1c acid, and more particularly in a process for concentrating.

' I portion of a dehydrating agent, such as sulphuric acid, is passed counter to a current of steam, or to a current of inert gases mixed with a large proportion ofsteam, over a laterally restricted path, sufliciently long to in sure the delivery at the outlet of vapors of highly concentrated nitric acid. Y

. The laterally restricted'p'ath is usually constituted-by a column of suflicient height, the mixed acids flowing into the top of the column, while the steam' or gases consisting largely of steam is or are introduced at the bottom. The rate of delivery of the gaseous medium, steam or steam laden gases, is regulated, and the column is bf a height such that nitric acid vapors of a high degree of concentration are delivered at the outlet.

The highest temperature is of course at the inlet ofthe hot gaseous medium, or just above this inlet, and the lowest temperature is at the inlet of the acids. The sulphuric acid 30 remains in the liquid state, and because of its affinity for water, practically all of the steam is taken up. With a path sufliciently long, in the presence of the sulphuric acid, the steam or vapor is condensed, leaving however the nitric acid in the gaseous state, and this con- A centrated nitric acidvapor may be conducted The process however does not work well- Applicationflled August 22, 1925. Serial No. 51,747..

ing treatment, large quantities of nitrogenous products.

With this object in view, I carryout the operation with conditions of temperature of the inflowing acids and the outflowi ng or exit gases, such that said gases are discharged at a temperature which will not exceed185 F and the conditions as to relativetemper ature I vary in accordance with theorganic matter content through a range of approximately 80 F. with the temperature increase inverse to the increase of organic matter content. That is for optimum operation, the higher the percent of organic matter present, the lower will be the temperature at the discharge for the gases at the top of the towers, and the lower the organic matter content, and the higher the percent of nitric acid, the higher Willbe the temperature at this discharge point. Exact temperature limits can- '7 not be specified, since as before stated the temperature is regulated in accordance with the amount of organic matter and nitric acid present. I

'A-longer path than that preferred in the treatment of acid substantially free from imurities such as organic matter, is advisable in the treatment of acids of the character in' question. A height of tower which should give good results is one of twenty diameters. 50

'That is a tower with the ordinary size of tower filling and with a diameterof two feet, should have a height of about 410'- feet, toobtain nitric acid of approximately 97% strength. A v It is advisable to return tothe circulation, that is to the.tower, the nitric oxids, which after passing the nitric acid condenser pass into the hypo-nitrite towers, and are there condensed to dilute nitric acid of say 35% strength. In my preferred procedure, the nitric acid of 35% strength from the hypoe nitrite towers is mixed with the incoming .nitro-glycerine waste acids fed to the tower. Such a procedure permits practically all of -3. The process'cfonc eniirating niti jc acid gpn'taining-organigmatter, which consist in 5- passi iig amix tui'e containing the nitric avid with rganicmatter; water, and-a liquid" de} 1. hydrating agenfi, ou1 1ter to" a current of a h t-jfgaseous'*inedium, cbmp'osed largely of :s tgam5 Over a relatively" long" path, andwith 50; a r'eliitivelr'ate of 'fgd of the-cold iacidszand the' hot steam, jsilchifiat t he tgmprature' of ,thei-exitfg'sfses' wi11 rangebetween 95;Efand 17 5 FL-,"gin inverse relation {t6 th'i'jorganic 155 1 Siglied'at- New York c'ity,-.in}th (:ountybf New'Yo'rkand State of New York, this, 19th da'y of AuguspA, 1)., 1925! I. 

